1. Field of the Invention
This invention relates to variable pitch mechanisms and/or propellers including such mechanisms and has been devised particularly though not solely for use in propellor driven aircraft.
2. Description of the Prior Art
Fan impellers, ground-adjustable propellers and flight-adjustable propellers are used on air-driven vehicles, wind-generating plants and windmills used for driving machinery, generating electricity and effecting irrigation, conducted fans and air conditioning systems. A propeller or fan impeller is a device having, or for mounting on, a revolving shaft with blades set at an angle to propel air in a desired axial direction. Ground-adjustable means for regulating the pitch of the blades are provided when the shaft is stationary, and flight-adjustable means for regulating the pitch of the blades are provided when the shaft is rotating and airborne.
In the prior art, with two or more bladed ground-adjustable propellers, the blades are individually retained in the hub and stopped from rotating around their longitudinal axes by means of a clamping device in the hub or due to an interference fit in the hub itself. To change pitch the clamping device or propeller halves have to be unlocked and the blades then adjusted. Each blade has to be set individually to the required pitch, the pitch setting checked by means of a visual reference, and the propeller hub then clamped up again. Pitch settings are generally done in the field and require considerable skill. A difference of one degree pitch setting between two blades can introduce unpleasant vibrations.